An Assembly is a Page?

I spent the better part of the day chasing down what was ultimately a check-box in Internet Explorer's Advanced options. Blech.

The problem was that IE was failing to load a user control, and not being very helpful in determining why the control wouldn't load.

The control would load properly using HTTP, but would fail under HTTPS. Sysinternals' Filemon and Regmon showed no anomalous behavior. Debugging with cordbg wasn't particularly useful - the information wasn't really pointing me anywhere. The IEHOST log file (http://support.microsoft.com/?kbid=313892) didn't provide much more than the fusion log, which contained:
*** Assembly Binder Log Entry (xx/yy/zzzz @ aa:bb:cc QM) ***

The operation failed.Bind result: hr = 0x80070002. The system cannot find the file specified.

Assembly manager loaded from: C:\WINDOWS\Microsoft.NET\Framework\v1.1.4322\fusion.dll
Running under executable C:\Program Files\Internet Explorer\iexplore.exe
--- A detailed error log follows.

=== Pre-bind state information ===
LOG: Where-ref bind. Location = https://localhost/path/assemblyname.dll
LOG: Appbase = https://localhost
LOG: Initial PrivatePath = bin
LOG: Dynamic Base = NULL
LOG: Cache Base = NULL
LOG: AppName = NULL
Calling assembly : (Unknown).
===

LOG: Processing DEVPATH.
LOG: Policy not being applied to reference at this time (private, custom, partial, or location-based assembly bind).
LOG: Attempting download of new URL https://localhost/path/assemblyname.dll
LOG: All probing URLs attempted and failed.

And yet the IIS log was showing that the assembly was being requested and returned successfully to the client.

Eventually, I encountered the following KB article:"How to run a user control assembly that is hosted on Internet Information Services (IIS) in Internet Explorer"
http://support.microsoft.com/?kbid=892466
which states:

"To successfully download a user control under these conditions, the client setting for the Do not save encrypted pages to disk setting must be cleared."

Simply clearing that check box allowed IE to download and instantiate the control.

Grumble.